This invention relates to uninterruptible power supplies that include a thermal energy source as a back-up energy source. More particularly, the power supplies of the present invention include a material that is heated and maintained at an elevated temperature during standby operations. In the event of a failure of the primary power source, such as utility power, the stored thermal energy is converted into electricity that provides the necessary back-up power until the primary supply comes back on line.
Uninterruptible power supplies (UPS) are well known. Such devices often are used to provide a nominal amount of power for a certain time period so that various pieces of equipment utilizing primary power may be shut down in a relatively normal fashion, rather than the instantaneous shut-down that would occur from a loss of primary power without a backup supply. One known configuration for a UPS is to provide a bank of chemical batteries as a short-term, secondary power source. The batteries often are combined with an emergency generator that provides long-term secondary power.
Chemical batteries suffer from various deficiencies including bulkiness, lack of reliability, limited lifespan (typically requiring replacement every 3-8 years), high maintenance costs and relatively low safety. For example, chemical batteries require relatively constant and complex recharging, depending on the type of batteries involved to insure that the batteries continue to operate efficiently and maintain their full storage capacity. Even well maintained batteries, however, may be unreliable due to a relatively high sensitivity to temperature. Additionally, chemical batteries raise various safety considerations due to the general nature of the large quantities of toxic and caustic chemicals involved. Typical large battery installations often require special venting and air-conditioning systems for the dedicated battery storage rooms.
In view of the foregoing, it is an object is of this invention to provide improved uninterruptible power supplies that provide back-up power from a thermal source of energy.
It is also an object of the present invention to provide improved uninterruptible power supplies that are relatively insensitive to ambient temperature variations while providing back-up power.
It is an additional object of the present invention to provide improved uninterruptible power supplies that have reduced maintenance requirements.
It is a still further object of the present invention to provide improved uninterruptible power supplies that have an essentially unlimited life cycle.